The present invention will be disclosed primarily in the context of lead acid batteries, however it will be understood that the background discussion and following discussion of particular embodiments of the present invention apply to a variety of battery devices beyond the lead acid battery-type.
Batteries undergoing charge and discharge cycles degrade to various degrees depending on the extent of discharge, nature of use, and the nature of the charging process in relation to the battery type. If quality batteries are properly sized and maintained, a battery system, e.g., a battery and associated charging and use circuitry, provides many years of reliable service. All batteries, however, do eventually age and degrade. The subject matter of the present invention extends the useful life of a battery and significantly improves its charging rate and capacity.
In the case of lead acid batteries, for example, each lead acid battery includes a plurality of battery plates with intervening electrically insulated separators therebetween. Each battery plate consists of a lead grid carrying a hardened lead oxide coating of a specific thickness. The battery plates stack alternately, positive next to negative, with a plate separator between each an adjoining pair of positive and negative plates. As a battery goes through multiple charge and discharge, cycles, the oxide coating and the lead grids eventually corrode and thin-out even with normal use. All batteries wear to some degree with each charge and discharge cycle. Excessive battery plate wear occurs, however, whenever a battery is deeply discharged followed by a significant delay in time between the deep discharge and a subsequent recharge. Very thin-plate batteries, such as those found in automobile battery systems, experience severe damage even with a single deep discharge followed by a significant, e.g., 24 hour, delay before charging.
Battery plate separators serve the same purpose in all batteries. The battery plate separator consists of a non-conductive barrier which allows low electrical resistance through the electrolyte, which in turn serves as a protective partition to prevent shorting across adjacent plates. The separator allows free ion flow between the adjacent plates for proper battery chemistry, i.e., to produce an electrical potential across the plates. Battery plate separators, however, do not always function as intended. The battery plate separators can act as a bridge which supports conductive matter causing plate shorting to occur. If plate separators functioned solely as intended, the battery would perform at a maximum potential, with normal plate wear as the main degradation process. Unfortunately, battery plate separators cannot prevent entirely undesirable electrical conduction directly between battery plates. To the extent that electrical conduction does occur between battery plates, battery operation diminishes both in charging rate and energy capacity.
In the case of lead acid batteries, a gradual decrease in battery capacity and charging efficiency occurs over the battery life. This decrease in battery capacity is considered the result of an increased number of minute shorts across the battery plates and through the plate separators.
An accumulation of lead hydrates in lead acid batteries is recognized as a mechanism establishing a limited degree of shorting of battery plates and degrading battery performance. Some battery charging systems provide an overvoltage, i.e., significantly above battery voltage, "equalizing charge" to clean the battery plates. Unfortunately, this method of "cleaning" a battery plate by overcharging causes a degree of damage.
Prior battery rehabilitation procedures and devices focus on the process of sulfation, a normal process occurring during battery discharge wherein sulfates tend to build up in crystalline formation within the battery. When the battery is later charged, however, the sulfates return to solution and again support chemical reactions producing an electrical potential within the battery. These prior battery rehabilitation processes and devices attempt to remove sulfates by application of fast-rise voltage pulses having amplitudes significantly larger than battery voltage. While various parameters of such voltage spike signals have been proposed, these prior procedures and devices by design attempt to establish a high voltage, relative to battery voltage, polarizing charge on the battery plates to dislodge sulfation material from the battery plates.